Just Another Puch E50 Dio Polini (Part 2: Intake And Exhaust Matching)

In Part 1, I matched the Polini cylinder to the case.  In Part 2, I will show how I matched the cylinder's intake and exhaust ports with the intake manifold and exhaust header.


PART 2:  INTAKE AND EXHAUST MATCHING



1)  I purchased the DIO manifold from TreatsHQ.  I was familiar with this manifold from my days of modifying Honda Elites back in college.  I still have one on my 1994 Dio motor with a 28mm Kehin carburetor attached to it.  I explored different ways on mounting the manifold to the cylinder.  I wanted to save as much heat sink fins on the cylinder that I could.  I thought of custom making the adapter plate out of plastic or aluminum. 

Motomatic Mopeds

After numerous trail and error and extensive web research, I ultimately decided on Motomatic Moped's Polini Maximizer.  I went this route due to lack of time and tools available to me at the moment.  I figured I start off with Motomatic's adapter plate and improve it from there.  Unfortunately, I had to hack off quite a bit of fins to get it to fit.  I used a hacksaw for this.  I also used the Dremel sanding bits to smooth everything out.

2)  Since I am going to use a 24mm carburetor for this build, I figured I should widen the intake ports on the Polini.  I didn't wanna go crazy and change the port timing.  So I ended up porting the intake ports about 3mm bigger towards the front of the cylinder.  I also spent some time cleaning up some of the casting imperfections.  I used various porting bits for this.  Take your time!!  Don't rush when it comes to porting.

I also used this time to port match the Dio manifold, adapter plate, and intake.  I corrected some of the adapter plate's misalignment.  I tried to ensure a smooth flow from the manifold to the adapter plate to the intake.  Take your time here too.  If you make a mistake just epoxy it up. 

3)  Smooth air/gas flow is the name of the two stroke game.  I got some great tips from a build I was reading on ZumaForums.net.  A builder from the Philippines named Overrun built a Yamaha Jog motor for his track race bike.  One of the tips was he used epoxy to fill up unnecessary voids in the crankcase to optimize the air/gas flow from the manifold to the crankcase.  Follow his build here (for some reason his pics are all broken linked so check out this build by Frank The Tank where he applies Overrun's tips).  I wanted to apply some of these concepts to this build.

It was time to match the manifold to the adapter plate and the adapter plate to the cylinder.  The Polini has a void space above the intake ports for its single reed to go into.  I filled this void with JB Weld.  Create a "form" (using masonry terms) with tape to block off the intake ports.  I took extra precautions and taped up inside the cylinder too in case of leakage.  Put junk screws in the screw holes.  Then pour the JB Weld like cement into the form.  Try to work the JB Weld around in the form to eliminate air bubbles.  Be sure to let it set for the recommended time or longer.  I didn't heat cure it or anything.  I let it cure at room temperature for about a week.  I seen this mod been done many of times on E50 Dio Polini builds (i.e. Magnum Dash).

After curing, sand down the epoxy using a flat edge and sandpaper.  I used a block sander used for car body repair work.  There were some air pockets I couldn't get rid of in the epoxy so I reapplied the epoxy and repeated the steps.

Intake

Intake

Since the cylinder's void was filled, I needed to match the adapter plate too.  I marked the where I had to fill and repeated steps above.  But before I filled it with epoxy, I scored the sides of the plate to provide some "profile" for the epoxy to grip on too.  I used my porting bits for this.  I tried to heat cure it under a lamp but burnt it instead.  But the integrity of the epoxy seemed to be not compromised.  Since the adapter plate was going to be sandwiched by the mainfold and cylinder, I wasn't worried about the epoxy cracking through or some air bubbles.  As long as there is a good surface area for the gasket it serves its purpose.

Top

Top

Bottom

4)  Mount the adapter plate onto the cylinder.  Correct any epoxy imperfections at this time.  Also, mount the lower half of the manifold.  Further match for a smooth flow.  Take note how the reeds open up into the intake.  Shape the epoxy for a direct flow as much as you can.

Shaped to a ramp

View through bottom half of the manifold with reed cage

Close up through the reed cage

View without the reed cage

Side view

Rear view

As you can see from the pictures above, the air/gas flow has a direct path from the manifold to the cylinder's intake. It kind of looks like a port type cylinder's intake in how it ramps toward the front of the cylinder. A thing to note is that the reed cage have metal "restrictors" on them to prevent the reeds from too much and breaking off. Use this as a guide to see the flow path to the cylinder. I could of added more epoxy to further funnel the flow base on the restrictor plates but decided not to at this time.

5)  Cut new gaskets. Be sure to take the time to match the gaskets to the modified holes. You took the time match porting everything, take the time matching the gaskets as well. Keep double checking your work. Get a hole punch set to make perfectly sized bolt holes. Believe me, it will make your life easier.

Intake to adaptor plate gasket

Adaptor plate to manifold gasket

After mounting the adaptor plate, I was considering filling the hex head bolt holes with JB weld to make it permanent. I decided against this just in case I wanted to use this polini kit with the malossi/polini reed cage set up instead. I opted to fill the holes with gasket sealer instead.

Ready for the gasket

Bottom half of Dio intake mounted:

Mounted and ready

6)  Match the exhaust port to the exhaust gasket.  Mark areas and match.  Spend some time cleaning out casting imperfections.  You can also spend some time polishing it to a mirror finish if you want.  It's not absolutely necessary.  I didn't port the exhaust port wider or anything.  I kept the stock port timing.  I'll run it first before porting out the exhaust. 

Exhaust gasket

Jolly Moto exhuast manifold

In PART 3:  TRANSMISSION WORK, I'll show all my transmission mods.

HAPPY TUNING!!